Synthesis of different types of energy based controllers for a Modular Multilevel Converter integrated in an HVDC link

Abstract

Modular Multilevel Converters are becoming increasingly popular with the development of HVDC connection and, in the future, Multi Terminal DC grid. A lot of publications have been published about this topology these last years since it was first proposed. Few of them are addressing explicitly the 2 different roles that are held by this converter in a HVDC link: controlling the power or controlling the DC voltage level. Moreover, for a given function, different ways of controlling this converter may be considered. This paper proposes an overview of the different solutions for controlling the MMC and proposes a methodology to synthesize the control architecture.

Global advanced control strategy for Modular Multilevel Converter integrated in a HVDC link

“…The resistors models the power losses within each arm and output filter are noted as R arm and R f , respectively. 14,26,27 The most accurate MMC model consists of thousands of nonlinear models of IGBTs and their antiparallel diodes. Four different models in reduced complexity are presented in Bergna et al 7 The MMC model type 1 considers a detailed representation of power switches.…”

“…On the DC side, the total energy and the balancing energy for each phase are controlled separably through the differential currents. 26,29 This cascaded control structure has several drawbacks such as stability problem and dynamic interaction between the inner and the outer loops.…”

“…In this part, we present a global control method based on the polynomial deviation state-space model (26). The control objectives of the MMC converter is to control the AC grid currents, the differential currents, the global stored energy, and the balancing energy between upper and lower arms.…”

Control of DC bus voltage with a Modular Multilevel Converter

“…Depends on the chosen solution the role of the grid current and differential current are exchanged. This issue is discussed and is simulated in [7] .…”

“…From this equivalent topology, it is possible to define an equivalent model which is very useful for the design of the two current controllers: control of the AC current, control of the DC current [7], [8].…”